How do I choose class intervals for a histogram

To choose class intervals for a histogram, first find the range by subtracting the smallest value from the largest value in your data. Decide on the number of classes (usually 5–10 for school-level data). Divide the range by the number of classes to calculate class width and round it to a convenient number (like multiples of 5 or 10). Then create equal, continuous, and non-overlapping intervals starting just below the smallest value.

Example: If your data is between 45 and 92, range = 47, number of classes = 6 → class width ≈ 8. Intervals can be:

40–48, 49–57, 58–66, 67–75, 76–84, 85–93.

This makes your histogram neat and easy to read.